A wide variety of implantable medical devices (IMDs) that deliver a therapy to or monitor a physiologic or biological condition of a patient, or both, have been clinically implanted or proposed for clinical implantation in patients. The IMD may deliver therapy to or monitor a physiological or biological condition with respect to a variety of organs, nerves, muscles or tissues of the patients, such as the heart, brain, stomach, spinal cord, pelvic floor, or the like. The therapy provided by the IMD may include electrical stimulation therapy, drug delivery therapy or the like.
The IMD may exchange communications with another device. The IMD may exchange communications with an external medical device, such as a programming device or a monitoring device (e.g., either attached to the patient or otherwise located near the patient). Alternatively, or additionally, the IMD may communicate with another implantable device, e.g., another device that forms part of an intra-body communications network. The information exchanged may be information related to a condition of the patient, such as physiological signals measured by one or more sensors, or information related to a therapy delivered to the patient. This information may be previously stored or real-time information. The IMD may also receive information from the programmer, such as configuration information that may be used to configure a therapy to be provided to the patient.
The IMD and the other device may exchange information using radio frequency (RF) communications. For example, the IMD and the other device may communicate in the 402-405 megahertz (MHz) frequency band in accordance with the Medical Implant Communications Service (MICS) band regulations. As another example, the IMD and the other device may communicate over the 401-402 MHz or 405-406 MHz frequency bands in accordance with the Medical External Data Service (MEDS) band regulations. In either case, the IMD and/or the other device with which the IMD communicates performs channel assessment to identify one of the channels of the particular frequency band to use for exchanging communications.